Portable electronic devices such as smartphones, tablet PCs, etc. are connected to external systems through, for example, a USB cable, and the batteries are charged with electric power from the external systems. The life span of batteries (e.g., Lithium-ion batteries and Lithium polymer batteries) shortens as the charging and discharging processes are repeated. That is, the time that a battery can be used is reduced. The internal cells of batteries are damaged by external impact. When a battery is nearly to a limited life or is damaged, which is called a ‘malfunctioning battery,’ the time that the battery can be used is extremely shortened. When a malfunctioning battery is charged, a swelling (a phenomenon that a battery swells) or an explosion may occur.